export function isIOS(){
    let u = navigator.userAgent, app = navigator.appVersion;   
    //let isAndroid = u.indexOf('Android') > -1 || u.indexOf('Linux') > -1; //android终端或者uc浏览器   
    let isiOS = !!u.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/); //ios终端   
    return isiOS
}